WCDMA uplink HARQ operation during the reconfiguration of the TTI length

Abstract

A method for minimizing the loss of data and ensuring that large delays do not occur during reconfigurations of an uplink transmission time interval (TTI) length of a WCDMA High Speed Packet Uplink Access (HSUPA) air interface, wherein the reconfiguration of an uplink TTI length is delayed until all pending retransmissions are successfully transmitted or until the maximum number of transmissions is reached. The transmission of new packets during this time period is prevented. However, pending retransmissions are allowed to occur. After the UE has received an ACK / NACK for each HARQ process, or until the specific maximum number of re-transmissions is reached, the UE starts transmitting with a new uplink TTI length.

Description

RELATED APPLICATIONS[0001]This application claims priority from U.S. Provisional Application Ser. No. 60 / 601,462 filed Aug. 13, 2004.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention generally relates to the Third Generation Partnership Project (3GPP) specification of the Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA) and, more particularly to, a method for minimizing the loss of data and ensuring that large delays do not occur during reconfigurations of an uplink transmission time interval (TTI) length of a WCDMA High Speed Packet Uplink Access (HSUPA) air interface.[0004]2. Description of the Related Art[0005]A key element of the HSUPA feature is high speed WCDMA Base Station (i.e., Node B) level Hybrid Automatic Repeat requests (HARQ), where the Node B immediately acknowledges the reception of transmitted packets at each uplink transmission time interval (TTI) subsequent to any propagation delays, such as Tpro...

AI Technical Summary

Benefits of technology

[0008]The invention is a method for minimizing the loss of data and ensuring that large delays do not occur during reconfigurations of an uplink transmission time interval (TTI) length of a WCDMA High Speed Packet Uplink Access (HSUPA) air interface. In accordance with the present invention, there are multiple techniques for ensuring that a system responds reasonably in the event of a change of the uplink TTI length. For example, a key element of Hybrid Automatic Repeat Request (HARQ) is that the transmission energy of unsuccessfully received packets is stored in a receiving device as soft symbols and a request for retransmission is sent as feedback information from the receiving device to the transmitting device. These soft symbols, which are obtained from different attempts to transmit the same packet, can be combined to create a single instance of the data packet. As a result, if a specific packet is transmitted twice and incorrectly received both times, then the incorrectly received packets can potentially be combined into a single correct packet. In one aspect of the present invention, the transmitted energy in the incorrectly received packets is not utilized, i.e., the soft symbols are not combined. In another aspect of the invention, the energy of the incorrectly received packets sent prior to the change in the uplink TTI length is used, i.e., the soft symbols of each transmission attempt are combined.

[0009]An incremental redundancy scheme is used to create a soft symbol. For instance, even though a transmitter transmits only hard bits (0 and 1, which are typically mapped to −1 and +1 by a radio), the receiver does not make a “hard” decision on whether it received −1 or +1. Rather, a decision is made with respect to how close the received bit is to −1 or +1. In accordance with the invention, the soft symbols of multiple transmissions can be summed together. As a result, the receiver can accumulate the transmitted energy from multiple transmissions. Here, the transmitter utilizes error correcting code and cyclic redundancy checking (CRC) check part in the transmission and in the receiver. After each attempt to transmit, the decoder makes a “hard” decision for each soft symbol. In addition, after decoding the received transmission, if the CRC check indicates that the data is correct, then the soft symbols can be cleared and the received, decoded packet can be relayed to the RNC. With incremental redundancy schemes, the transmitter may partially transmit different bits in each transmission. In addition, the receiver has prior knowledge of which bits should be transmitted in each attempted transmission.

Problems solved by technology

As a result, a delay is imparted to the reconfiguration of the uplink TTI length.

Images